@Test
 public void testMin() {
   CategoryColumn categoryColumn = CategoryColumn.create("US States");
   categoryColumn.addAll(TestDataUtil.usStates());
   assertTrue("Alabama".equals(categoryColumn.bottom(5).get(0)));
 }
 @Test
 public void testMax() {
   CategoryColumn categoryColumn = CategoryColumn.create("US States");
   categoryColumn.addAll(TestDataUtil.usStates());
   assertTrue("Wyoming".equals(categoryColumn.top(5).get(0)));
 }